Child tax credits are based on earned income. If you have no earned income then you are not eligible for any type of tax credit based on earned income.
SSI is Supplemental Security Income and is not from the Social Security Administration. It is designed to help aged, blind, and disabled people, who have little or no income; and. It provides cash to meet basic needs for food, clothing, and shelter. SSI is not reported on a tax return.
Social Security Retirement/Disability/Survivors benefits are reported on a form SSA-1099 and the benefits received are reported on a federal tax return. The benefits may be taxable depending on the amount of other income you have entered on your tax return.
However, if the Social Security benefits are the Only income to be reported on the tax return, then there is no reason or need to file a tax return.